The FAA expects the U.S. commercial drone fleet to grow from 42K at the end of 2016 to about 442K aircraft by 2021 (but there could also be as many as 1.6M commercial drones in use by then).

The key difference in its growth estimates is in “how quickly the regulatory environment will evolve, enabling more widespread routine uses of (drones) for commercial purposes.”

Since August, the FAA has approved more than 300 waivers for drone use without some restrictions for firms including Union Pacific (NYSE: UNP), BNSF Railway ( BRK.A, BRK.B), Intel (NASDAQ: INTC), Walt Disney (NYSE: DIS) and Time Warner (NYSE: TWX).